The present invention relates to the art of pickling metal sheet material and, more particularly, to improved apparatus for pickling a continuous length of metal sheet or metal plates.
It is appreciated that the present invention can be used for pickling, cleaning, etc. of various metals as the metal is moved along a generally horizontal process path; however, the invention is particularly applicable to pickling a continuous strip of stainless steel by acid and will be described with respect thereto. This description is representative in nature. The invention can be used for discrete plates of metal passing along a generally horizontal path. Some aspects of the invention can be used for sealing a support, dam and/or drive roll of a chemical tank.
It is of course well known to pickle metal sheet such as stainless steel, for the purpose of removing surface oxide and scale from the metal sheet, by passing the sheet through a grid work of electrodes in an electrolytic pickling tank an/or through an acid pickling tank. Heretofore, apparatus for pickling a continuous length of metal sheet material, such as stainless steel strip, included a relatively deep tank structure in which the metal sheet followed a generally U-shaped path between pairs of rolls at input and output ends of the tank. Frequently, a center roll or rolls at the lower end of the U are necessary in order to hold the strip down in the tank. Such a relatively deep tank structure requires a considerable amount of pickling solution to fill the tank. In connection with the electrolytic pickling of a continuous strip, which is generally used for non-stainless steel strip, the tank includes electrodes through which the metal sheet passes. When it is necessary to drain the pickling solution from the tank, it is necessary to stop the process and movement of the metal sheet through the tank. Further, feeding the metal strip through the tank along a U-shaped path imposes relatively high tension on the strip, especially if center rolls are employed to hold the sheet down in the tank.
All of the foregoing problems affect the cost of the pickling equipment, the cost of the pickling operation using the equipment and/or the quality of pickling of the sheet material or plate being processed.